1. Field of the Invention
The present invention relates to variable resistors and, more particularly, to a driving mechanism for variable resistors, which allows contactors movable by an operation lever to be normally held in a predetermined position on resistance elements when the lever is not operated. The output value of the resistor can be varied when the lever is operated, but the lever will be returned automatically to its original position when the force moving the lever is released.
2. Description of the Prior Art
A variable resistor for controlling servomechanisms, which has a sliding contact member in contact with a resistor element and capable of being automatically returned to the central position is known. When the sliding contact member in such a variable resistor is returned to the central position, the output thereof is zero volt.
A variable resistor provided with a spring as a means for automatically returning a sliding contact member is known, for example, as described in Japanese Laid-Open Pat. No. 86667/1975.
However, known variable resistors, such as that described in the above-mentioned Japanese patent, have to be provided with a grounding means and they have a complicated construction. Moreover, they have a large number of parts and are very difficult to assemble.